The invention relates to a device for pivoting the knife in its longitudinal axis and for adjusting the knife depth on knife folding machines having disposed between drive motor and knife drive a coupling and brake unit for the upwards and downwards movement of the knife bar guided in a housing pivotable in the direction of rotation of the drive.
In the case of such a known apparatus, the knife bar is guided in a housing which has a shoulder projecting into an inner shoulder on a housing arm and which is so rotatable in respect of the housing arm that the knife is pivoted in its longitudinal axis. The adjusted position of the housing in respect of the housing arm can be fixed by means of a locking screw. Disposed in the housing arm are the drive elements which at the housing end terminate in a disc having disposed in it an eccentric stud which engages a sliding member mounted on the knife bar, so that the rotary movement of the drive unit is converted to the to-and-fro movement of the knife bar. The housing arm has parallel with the extension of the housing a holder which at its free end and at the height of the folding rollers with which the knife co-operates, is articulated on a housing part at a joint on which there is also mounted an adjusting screw having a threaded seating and the end of which actively engages the holder in the direction of the axis of the housing arm. Upon an adjustment of the setscrew, the arrangement comprising the housing, the housing arm and the holder is pivoted about the pivoting stud on the housing which leads to an adjustment of the knife depth which by reason of the considerable pivoting radius can in its direction of action be regarded very closely as a linear displacement of the knife (German Offenlegungsschrift No. 25 04 489).
It is true that the known device permits of a negligible adjustment of the knife depth while the machine is running but this adjustment is linear only over very minimal height differences so that upon pronounced adjustments alignment of the folding roller gap in relation to the knife is guaranteed only if the knife held in a clamping mounting on the knife bar is realigned by being pivoted about its longitudinal axis, which can in turn be undertaken only while the machine is stationary. Also rotation of the housing in respect of the housing arm can be carried out, once the locking screw has been undone, only while the machine is stationary, since via the guide of the knife bar, the housing is acted upon by drive forces which do not permit of an accurate and reliable adjustment of the housing in relation to the housing arm while the machine is operating.
To regulate the length of the knife adjustment in the case of a sheet folding machine while it is in operation, it is furthermore known to mount on the end of a long supporting arm which bridges the major part of half of the sheet to be folded in extension thereof a parallelogram guide for the folding knife. Acting upon the parallelogram guide, in order to lift the knife, is a pull rod, the effective length of which is adjustable (German Pat. No. 932 428).
It is indeed possible with this known and structurally complicated device to adjust the knife depth even while the machine is operating but pivoting of the knife in its longitudinal axis is not however possible.